LOS ANGELES — Los Angeles Mayor Eric Garcetti explained his decision to sit out the 2020 presidential contest in simple terms — the city, he said, "is where I want to be."

The challenges in front of him were obvious.

Already overshadowed by the White House run of his fellow California Democrat, Sen. Kamala Harris, the low-key mayor in his second term would have faced a long list of obstacles that would come with trying to manage a city of 4 million while mounting a national campaign in states where he is virtually unknown.

The Democratic field is growing crowded with bigger names, including Sens. Elizabeth Warren of Massachusetts and Kirsten Gillibrand of New York, with more expected to enter the race. Garcetti would have contended with an ominous historical barrier — no mayor has ever won a major party's presidential nomination. And he would have needed to explain why he should be in the White House with L.A.'s downtown streets lined by homeless encampments and freeway traffic often at a standstill.

Only recently, he had suspended his consideration of a 2020 bid during a teachers strike, a sign of the diversions that would come with trying to be a mayor-candidate.

Talking with reporters Tuesday at City Hall, Garcetti waved off the suggestion that Harris' presence in the race had discouraged his interest in challenging President Donald Trump. As a candidate, he would have been competing with Harris for donors in Hollywood, organized labor and business, while fighting for votes in their shared home state, where the primary is planned for early March 2020 alongside a gaggle of Southern states.

After ending months of speculation about his political future, he said he was proud of Harris but that her candidacy had no influence on his decision. You have to "listen to your own heart," he added.

The timing of Garcetti's announcement came as something of a surprise. The 47-year-old mayor sounded like a presidential candidate as recently as last week, using a national conference of his fellow mayors to criticize Trump in a speech delivered blocks from the White House. He lamented a divide between "Washington and the rest of us."

But on Tuesday, Garcetti said Los Angeles "is where I want to be and this is a place where we have so much exciting work to finish."

"I kind of believe that whenever possible, you should finish the job that you set out to do," he added.

Garcetti raised his national profile in 2018 by campaigning and raising money for Democratic candidates and state parties around the country. His $2.5 million-plus in party fundraising included $100,000 each for the state parties in each of the first four presidential nominating states of Iowa, New Hampshire, Nevada and South Carolina. He made stops in several of those states and other longtime battlegrounds like Ohio, where he frequently talked about the city's transit-building boom

Even bowing out, Garcetti could remain a key figure for the party, eventually being a surrogate for the nominee or perhaps a vice presidential running mate. He could also position himself for a Cabinet post — particularly secretary of transportation or housing and urban development — should a Democrat ultimately prevail.

Garcetti defended mayors as good presidential candidates, saying their experience as chief executives squared well with the job in the White House. Former New York Mayor Michael Bloomberg still is weighing a run, and former New Orleans Mayor Mitch Landrieu is also mentioned as a potential candidate, though he has not made the recent moves of someone positioning himself for a run.

Asked about whether he would pledge to complete his term at City Hall, Garcetti was noncommittal. He also steered around a question about whether he'd be interested in becoming vice president, quipping that he had a better job at City Hall.

"Who knows what the future is," he said, adding later, "Life is long."